“It was always the plan. Married couple on the TARDIS and seeing what that was like. And the Doctor with the married couple, standing in the control room thinking, ‘What have I done?’”

If the fans at that event were any indication, it’s no secret that Rory is loved—but why exactly?

Rory has a good head on his shoulders, I’ll give him that, but he’s not very brave or exceptionally adaptable or even a little bit dashing. Most Doctor Who companions have one or two of these traits, or they’re geniuses in their own right, and it’s easy to understand why the Doctor brings them along. But Rory is not another Mickey Smith either; he’s not an idiot kid whose journey is dependent on him growing up, toughening up and getting serious. In fact, Rory’s importance on the TARDIS is fairly easy to sum up:

Rory is there for Amy.

Keeping that in mind, the latest episode, “The Curse of the Black Spot” served as a touching reminder about why Rory belongs there and why a married couple on the TARDIS was an absolutely fantastic idea.

It has been noted in numerous interviews that one of Amy’s problems character-wise is that she can be just as crazy as the Doctor. She doesn’t have that moment where she presses the “is this a good idea?” button in her brain, poor girl. We can tell from her actions on the series and the stories about short skirts and kiss-o-grams, that it gets her into trouble a lot. (Need I remind you that she did recently don a tricorner hat and cutlass and try to fight off an entire crew of pirates with absolutely no sword training whatsoever?) So why did she marry Rory? Staid, sensible, my-idea-of-an-adventure-is-probably-trivia-night-down-at-the-pub Rory?

Simply put, Rory keeps Amy tethered to reality. He reminds her to live in the tangible world by being a practical anchor and also by being vulnerable (whether he likes it or not). When they were young, she claimed her life was boring before she found Rory. He would play “Raggedy Doctor” with her, and was probably the one to comfort her after every therapist she bit. Strange though it may seem as a foundation for a relationship, it’s safe to assume that he kept Amy from doing some more unpleasant things to stave off boredom during their childhood.

Then when she starts traveling in the TARDIS, the Doctor brings Rory on board to remind Amy that she still has a real life back home. I think it speaks volumes that the Doctor has never done this for a companion before in the history of the show. It’s clear that he bears Rory’s pleas for sanity and occasional lecturing because he knows how important he is for Amy (and because the Doctor likes the guy—he doesn’t reserve monikers like “Rory the Roman” for just anybody).

Rory’s vulnerability makes the stakes of every adventure real. Without him, Amy goes wandering past “Keep Out” signs with no thought of the consequences. But, send a siren after Rory and suddenly Amy is protecting someone; she can’t just throw herself into harms way for the fun of it. She’s not a teenager at the wheel of her first car anymore, she’s an adult with important people in her life who need her.

What is interesting about this dynamic is how the Doctor has handled the change. He seems to have decided that in order for this to work aboard the TARDIS, the married couple have to be each other’s responsibility rather than his. It begins when Rory first snaps on the Doctor regarding Amy’s safety in “Vampires of Venice,” and the Doctor—for the first time on the show—calls someone out for making everything his fault. An understanding seems to develop between he and Rory from that point on: traveling with him is their choice and he can’t be the one who gets shouted at every time something goes to pot.

That doesn’t mean that the Doctor will never rescue them when they’re in peril, but it does change the structure of each trip for the couple. The episode “Amy’s Choice” is just what the title says; at the end, the Doctor lets Amy decide for both of them which reality is the true one. What’s more, he allows her to make that choice based on a completely emotional revelation—that she doesn’t want to live without Rory.

During the series 6 opener, when the Doctor tries to tell Rory that Amy can’t hear him through her lost nanorecorder, Rory explains, in short order, that his connection with Amy is not dependent upon fancy Time Lord technology. He promises Amy that he is bringing the Doctor to save her. Because the responsibility is his.

In “The Curse of the Black Spot,” the strengthening of their relationship comes across more powerfully than ever. Rory asks Amy to perform CPR to save his life because he knows she won’t give up on him (the implication being that the Doctor eventually would). And sure enough, while Amy is desperately attempting to revive Rory, the Doctor is sitting there on the side, watching in horror. He is, in point of fact, doing exactly what Moffat said he would be doing—standing there thinking, what have I done?

What he has done, surprisingly enough, is take what might have been an otherwise tenuous marriage between two very young people and reinforced it with steel and duct tape and super glue. Because as long as Rory and Amy are responsible for each other, as long as they have to look out for each other, the closer they will become. All the doubt on Rory’s end, all the fear and flighty-ness on Amy’s end, will cease to matter the more they are forced by circumstance to prove how much they mean to one another.

By accident or design, the Doctor has brought two people closer together by virtue of his frenetic lifestyle. Looks like that TARDIS is a pretty good place to honeymoon.

Emily Asher-Perrin wants people to start calling her Emily the Roman. You can bug her on Twitter and read more of her work here and elsewhere.